1. Field of the Invention
The present invention relates to a water-cooled vertical engine having a crankshaft disposed substantially vertically and having water jackets provided independently in a cylinder block and a cylinder head, and an outboard motor equipped with the water-cooled vertical engine.
2. Description of the Related Art
As a vertical engine for an outboard motor, a water-cooled engine is generally used. In this type of water-cooled engine, when a cylinder block and a cylinder head are equally cooled with cooling water, if the cylinder head, which generates a comparatively large amount of heat, is cooled to an appropriate temperature, then the cylinder block, which generates a comparatively small amount of heat, tends to be overcooled. An outboard motor cooling structure that can solve such a problem and cools both the cylinder head and the cylinder block to appropriate temperatures is known from Japanese Patent Application Laid-open No. 61-167111.
In embodiments and modification thereof described in this publication (ref. FIG. 2, FIG. 2a to FIG. 2c, FIG. 3, FIG. 3a and FIG. 3b), by supplying low temperature cooling water from a cooling water pump to a cylinder head water jacket and supplying the cooling water having its temperature thereby increased to a cylinder block water jacket, the cylinder block is prevented from being overcooled while the cylinder head is cooled sufficiently.
However, in the above-mentioned conventional arrangement, since the water jacket for the cylinder head and the water jacket for the cylinder block are connected in series, and cooling water passes through the water jacket for the cylinder block after passing through the water jacket for the cylinder head, it is difficult to control the temperature of the cylinder block and the temperature of the cylinder head independently at appropriate temperatures.
Furthermore, the cooling water pump is generally provided beneath the cylinder block, and if cooling water is supplied via an external pipe to the cylinder head water jacket, which is separated from the cooling water pump, there are the problems that the number of components increases and sealing is troublesome.